One may imagine a simple device, as shown in FIG. 5 (prior art). A metal tube 12 is in vertical orientation. The metal tube 12 is filled with a small amount of working fluid. A heat sink 14 is mounted on an upper side of the metal tube 12. A heat source 16 is applied to the lower side of the metal tube 12. The working fluid will evaporate, while cooling the heat source 14. The vapor 18a will move up, and condense near the heat sink 14. From there, the working fluid 18b drips back to the lower side of the metal tube 12.
In this model heat pipe, the working fluid 18b simply drips back to the heat source 16. It is quite obvious that this design will only work in vertical orientation. To overcome this limitation, commercially available heat pipes do not rely on gravity alone to move the working fluid back to the heat source.
One of such heat pipes may include a mesh defining a number of pores. A decrease in size of the pores may promote the generation of a capillary force. The capillary force drives the working fluid to the heat source. However, such decrease is limited because each of the pores of commercially-available meshes has a diameter more than about 1 micrometer.
What is needed, therefore, is a heat pipe including pores, wherein each of the pores has a diameter less than 1 micrometer.